Like detectives working with ancient clues, Professor
Johann Peter Gogarten and his students use modern
genetic tools to illuminate the early days of life on
Earth, a period that dates back 3.8 billion years.

Peter Gogarten, left, professor of molecular
and cell biology, with Olga Zhaxybayeva, a
graduate student who works in his lab.

Photo by Dollie Harvey

A molecular biologist by training, Gogarten studies
the evolution of microorganisms from the very dawn of
time. His work is challenging beliefs that have long
been bedrock biology, ever since Darwin introduced
the concept of species evolution as a steadily
branching "Tree of Life."

Since 1989, Gogarten has been taking molecular and
cell biology students at UConn on a journey that
might have been imagined by H.G. Wells. His classes
focus on molecular evolution and molecular biology,
often through the world of so-called "simple"
one-celled life forms - whose not-so-simple genome
would take 400 pages if printed out.

Students learn how more complex organisms came about,
and how proteins - the main component of cellular
machinery - arose early in life, and how they arise
today.

"The goal of my classes is to prepare biologists for
the genomic age," Gogarten says.

Gogarten was among the first to recognize that
horizontal gene transfer is so frequent that the Tree
of Life paradigm is in trouble. Horizontal transfer
of genes differs from the traditional way of
inheriting traits "vertically" from a parent or
ancestors.

Lateral transfer, Gogarten and other scientists say,
created the machinery that is used by bacteria to
perform oxygen-producing photosynthesis. About 2,300
million years ago, this photosynthetically produced
oxygen changed the face of our planet, poisoning many
organisms living at the time, while allowing the
emergence of other organisms that use oxygen in
respiration. Today's multicellular organisms became
possible only through the large amounts of energy
gained in respiration. An analysis of five
photosynthetic types of bacteria by Gogarten's lab
showed that gene transfer was instrumental in
inventing oxygen-producing photosynthesis. This and
other analyses contributed also to thinking that the
Tree of Life wasn't really a tree at all.

"It's more like a network than a tree, given that
horizontal gene transfer is taking place among very
diverse organisms," Gogarten says. "In the world of
animals, that would be like a giraffe sharing its
genes with an elephant to produce a long-necked
elephant that could graze for leaves at the top of
trees. That doesn't happen with animals, but things
like that do happen all the time with bacteria and
other microorganisms."

The study of how genes can pass between divergent
organisms not only brings evolutionary activities
from eons ago into sharper focus; it also assists
with modern issues that touch on botany, medicine,
and food production.

Consider, for example, the implications of the
mischievous behavior of a soil-borne pathogen called
Agrobacterium tumefaciens. It enters a plant through
a wound site and inserts a segment of its own DNA
into the plant's genome. The transferred genes cause
a tumorous proliferation of plant cells that instruct
the plant to produce compounds containing the carbon
and nitrogen on which Agrobacterium lives. While this
transfer from single-celled to multicellular organism
is rare, it occurs on a regular basis between
microorganisms.

A native of Germany, Gogarten began studying how
cells take up molecules from their environment as a
graduate student. He looked deeper into the issue and
soon was pondering a related topic, the evolution of
proteins that function as transporters. "Since then,
I've been hooked," he says.

Because fossil evidence from 3.8 billion years ago is
scarce, Gogarten and his students use genes and
genomes from present-day organisms and extrapolate
backwards using specialized computer programs. The
professor's website is filled with resources and
links, as well as quizzes and a section that allows
students to ask him questions about complex topics as
gene sequencing, taxonomic groups, and genetic
algorithms.

Gogarten's students often continue in academia, or
they find a professional home in the pharmaceutical
industry, working perhaps in gene therapy or drug
delivery system research, or devising ways of
breeding better crops using genetic and genomic
research.

Much of the activity in Gogarten's laboratory is
focused on the origin of eukaryotes, the kingdom of
life that includes all the higher plants and animals,
including humans. Microfossils in sedimentary rock
dating back 3.8 billion years reveal microscopic
colonies of what might be called bacteria. But if
they were already abundant then, where did they come
from and what was their ancestor?

Questions like these are leading Gogarten and other
researchers around the world to redraw Darwin's Tree
of Life in a very different way.

The three forms, or domains, of life are bacteria
(including those capable of photosynthesis),
eukaryotes, and archaea, another type of bacteria.
There may have been two primary lines of descent, the
common bacteria on one branch and the archaea and
eukaryotes on the other. Researchers in Gogarten's
lab discovered that the three domains of life arose
through a different series of steps than had
previously been believed.

Around the world, Gogarten and his colleagues pore
through massive databases, analyzing and comparing
the genomes of different life forms invisible to the
naked eye, trying to shed light not on one of the
great mysteries of life, but literally on the great
mystery of life.

The relationships among these microscopic, one-celled
organisms go beyond "elusive" for most people. But
Gogarten, his students and colleagues around the
world are patient, persistent, and dedicated, knowing
they are part of a scientific endeavor that really
began only in the 17th century, when Anton Van
Leeuwenhoek, a Dutch lens maker, first stared through
a simple microscope at mysterious microbes. Centuries
later, their relationship to mankind continues to
fascinate.